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Old 24th September 2005, 10:21 AM   #21
icebear is offline icebear  Norway
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Hi Freddy

Im running them up to 66 hz (48 dB Butterworth filter) Otherwise it's to much voice in them. It's easy to hear when I sit in the sweetspot and adjust the X-over while playing (Behringer DCX 2496 and laptop)

There is a good punch no matter what you play. And the bass is liberated as dipoles are at the low notes.

The wings don't flex much at all. It has the same vibration as the cabinet itself.

I have not been looking at the Reams Karlson-hypex patent.

I'll try to explain how the Forsman system works:

The goal for the Forsman project was to overcome the shortcomings in the existing speakersystems. The speaker should have the dipoles speed, the boxspeakers size and the linespeakers beampattern. The last one do not wast energy to the roof and floor. So they looked at the Karlson system. It did not suit them perfectly so they had to develop it further. They made a split at each side og the baffle, and the Vertical Split System was born. Their assumptions regarding to pulsqualities turned out to be true. It was confirmed by companies like Bruel & Kjr.
By making the volume in front of the element small, a pressure rise will occure ( ca 20dB at the most narrow part of the split). The pressure decrease as the split gets wider. By placeing an element in the widest part of the spilt it will not be obstructed by the spilt and will beam free. In the more narrow part of the split it will gain a pressure rise, and it will hold up to 35-45 cm in front of the opening. A pressure rise is harder to outcancle than just an low frequent beam.
If you do the same at the backside, just turned 180deg, you'll get to sets of pressure areas. The distance between the pressure areas will be the speakers height, pluss the area of a curves baffleplate around the elements. The result is a folded acoustic dipole, like antennatechnik.


http://www.forsman.no/?page=produkt#virkemate

Click the image to open in full size.

The size I have on my set is 38cm (w) * 38cm (d) * 45 (h)
Mybe not ideal.

rgds
Bjrn
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Old 24th September 2005, 10:35 AM   #22
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Quote:
Originally posted by AJinFLA
I didn't forget you John, your site was the first link in my original reply
But what to make of the pic above your post? The Karlsonpole? Resonance anyone?
At least I like his wood working skill and craftsmanship. That looks a lot like mine.

Cheers,

AJ

Hi AJ,

Yes I saw you referenced my geocities site. Thanks. I just wanted to point directly to the M&D pages since the info there is a little better presented.

As for the Karlsonpole, Can't response since I haven't looked into such designs. I guess I feel like you. Why take a simple design and make it complicated? I'm sort of guilty of that myself with the U-frame, but there are distince advantages and disadvantages of the U compared to an H. If the Karlsondipole works for the builder then that's what matters. Not my cup of tea though.
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Old 24th September 2005, 11:52 AM   #23
freddi is offline freddi  United States
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Hi Icebear and JohnK

I've not seen dB quote for pressure-rise at narrow portion of slot -

heres a near-aperture plot of a regular vented K-coupler (not k15)

slower slopes is with mic torwards tight portion

Click the image to open in full size.

Karlson can (on good day) play pretty smoooth and high impact bass and for some reason cone excursion seems low - why?

(what size should a Karlsonpole be for 15" drivers?)
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Old 1st May 2006, 03:47 AM   #24
snkby is offline snkby  United States
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Default theres an entire aspect of the k-slot that

is not being addressed.

the k-slot acts as an impedance matching transformer between the drivers and the room.

in a k-slot the impedance of the volume in front of the drivers is far less than the impedance of the entire room.

like with a horn its not really the driver playing into the room its the square area of the mouth that plays into the room.

so with a k-slot its not really the driver that plays into the room but the area of the slot itself.

imagine the slot as a membrane with the mass of air.

this is where the step-response acuity comes in.

forsman claims a driver response time up to 80% faster when loaded into a k-slotted tube.

ideally the impedance behind the driver should be the same as in front of the driver.

i have built many k-slotted tubes with many different drivers and can attest the increase in response time and linearity.

so much so that i remember having to remove tweaks made to some fullrange drivers when placed into the k-slotted tubes.

the k-slotted tubes just smoothed everything to the point that many different sounding drivers on an ob sounded very similar in the k-slotted tubes.

the k-slot also acts as a wide-bandwidth filter/waveguide by allowing frequencies to exit the slot only as their wavelength allows.

anyway thats how it was all explained to me by people with a lot more acoustics knowledge than i have.

at a diy speaker meeting a few years ago siegfried linkwitz took a look at the interior of my 15"dia pvc k-slotted tubes and with eyebrows raised and in his german accent said *that is a very complicated structure !*

i have also had success in *boffling* ala hartley the rear wave to achieve better bsc.

some trade-off in step-response/impedance coupling and also room placement.

but everything in audio is a compromise anyway just a matter of how much of what where.

glad to see people experimenting with k-slots and k-slotted tubes.

i am about to put an 80"planar line-array into a 12"dia mirrored k-slotted tube that will also be boffled.

although it will now have to wait until we move this month.
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Old 1st May 2006, 03:50 AM   #25
snkby is offline snkby  United States
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Default hey freddyi ! didnt see your

question abou the 15" driver.

forsman uses a 2:1 ratio of driver diameter vs tube diameter for their bass drivers.

so ideally a 15" driver should have like a 30" diameter tube.

let me know if you need a plot !
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